Difference Between Flocculated and Deflocculated Suspension

Main Difference – Flocculated vs Deflocculated Suspension

A suspension is a state of a substance in which the particles of a substance are mixed with a fluid but are undissolved. Suspensions can be divided into two groups as flocculated suspensions and deflocculated suspensions based on electro-kinetic nature of solid particles that are suspended in the suspension. In chemistry, flocculation is the process in which colloids in a suspension can be obtained in an aggregated form. These aggregates can undergo sedimentation by settling down to the bottom of the liquid. The main difference between flocculated and deflocculated suspension is that the rate of sedimentation in a flocculated suspension is rapid whereas the rate of sedimentation in a deflocculated suspension is slow.

What is a Flocculated Suspension

A flocculated suspension is a suspension in which particles of the suspension has undergone flocculation. Flocculation is the process in which colloids in a suspension can be obtained in an aggregated form. Therefore, a flocculated suspension is composed of large aggregates and this type of suspension will lead to a rapid rate of sedimentation.

Sedimentation is the settling down of aggregates or particles of suspension to the bottom of the liquid. Aggregation of particles makes large aggregates that can act as large individual particles. When these aggregates are settling down, a large number of particles are settling down. Then the rate of sedimentation is high. These aggregates are known as floccules. Floccules can sediment faster than smaller particles under the effect of gravity.

The sediment formed in a flocculated suspension is larger than expected because the floccules have a loose structure with pores and these pores can entrap liquid. Therefore the volume of the final sediment is larger than expected.

What is a Deflocculated Suspension

A deflocculated suspension is a suspension in which no flocculation has taken place. Hence, there are no floccules or other aggregates. Here, single colloid particles act as individual particles. When sedimentation occurs, these single particles settle.

In a deflocculated suspension, dispersed particles exist as separated units. The rate of sedimentation is slow since smaller particles are settling rather than large floccules. The slow sedimentation prevents the liquid from being entrapped in the sediment. The final sediment has a small volume than a flocculated suspension. Even after the formation of the sediment, the supernatant of this suspension will still have a cloudiness.

Figure 1: Flocculated and Deflocculated Suspension

The formation of the sediment here is also called caking. The re-dispersion of this sediment (from slow sedimentation) is difficult even with agitation.

Degree of Flocculation

Degree of flocculation is the ratio between the sedimentation volumes of flocculates suspension and the deflocculated suspension.

β = F / Fβ

Where β is the degree of flocculation, F is the sedimentation volume of flocculated suspension and Fβ is the sedimentation volume of deflocculated suspension.

Difference Between Flocculated and Deflocculated Suspension

Definition

Flocculated Suspension:A flocculated suspension is a suspension in which particles have undergone flocculation.

Deflocculated Suspension:A deflocculated suspension is a suspension where no flocculation has taken place.

Floccules

Flocculated Suspension:A flocculated suspension has floccules.

Deflocculated Suspension:A deflocculated suspension has no floccules.

Rate of Sedimentation

Flocculated Suspension:The rate of sedimentation in a flocculated suspension is high.

Deflocculated Suspension:The rate of sedimentation in a deflocculated suspension is low.

Volume of Sediment

Flocculated Suspension: The volume of sediment in a flocculated suspension is high.

Deflocculated Suspension:The volume of sediment in a deflocculated suspension is less.

Porosity of Sediment

Re-dispersion

Flocculated Suspension:The re-dispersion of a sediment formed in a flocculated suspension can easily be done by agitation.

Deflocculated Suspension: The re-dispersion of a sediment formed in a deflocculated suspension is difficult by agitation.

Conclusion

A suspension is also called a dispersed system since there are particles all over the liquid. Flocculation is the formation of floccules in a suspension. That can happen spontaneously or due to the presence of flocculating agents. There are suspensions that can be either flocculated or deflocculated. The main difference between flocculated and deflocculated suspension is that the rate of sedimentation in a flocculated suspension is rapid whereas the rate of sedimentation in a deflocculated suspension is slow.

About the Author: Madhusha

Madhusha is a BSc (Hons) graduate in the field of Biological Sciences and is currently pursuing for her Masters in Industrial and Environmental Chemistry. Her interest areas for writing and research include Biochemistry and Environmental Chemistry.